Cementing plug release assist apparatus

ABSTRACT

Apparatus for assisting the release of a cementing plug positioned within the upper cylindrical cavity of a continuous cementing head plug container during the cementing of an oil well casing string or the like. The apparatus includes a threaded body for connection with the upper end of the plug container and carries an extendable and retractable scissors type linkage on the lower end thereof extending downwardly into the plug container cavity to contact the cementing plug. The downward extension of the linkage is activated by an upwardly spring biased rod carried within the body and connected to the upper end of the scissors linkage. Also disclosed is a rod retaining and releasing apparatus for releasably securing the linkage in the retracted position, an indicator apparatus for visually indicating the extension of the linkage and the release of the cementing plug from the plug container into the casing string.

United. States Patent 1191' Streich Feb. 4, 1975 CEMENTING PLUG RELEASE ASSIST [57] ABSTRACT APPARATUS Apparatus for assisting the release of a cementing plug [75] Inventor: Steven G. Streich, Duncan, Okla. positioned within the upper cylindrical cavity of a continuous cementing head plug container during the ce- [73] Asslgnee' ga g Company Duncan menting of an oil well casing string or the like. The apparatus includes a threaded body for connection with [22] Filed: Apr. 5, 1974 v the upper end of the plug container and carries an ex- I tendable and retractable scissors type linkage on the [21] Appl' 458l97 lower end thereof extending downwardly into the plug container cavity to contact the cementing plug. The [52] US. Cl. 166/70, 166/85 downward extension of the linkage is activated by an [51] Int. Cl E2lb 33/05 upwardly spring biased rod carried within the body [58] Field of Search 166/70, 85, 153 and connected to the upper end of the scissors linkage. Also disclosed is a rod retaining and releasing ap- [56] References Cited paratus for releasably securing the linkage in the re- UNITED STATES PATENTS tracted position, an indicator apparatus for visually in- 1,763,642 6/1930 Dievendorff et al... 166/70 dicafing the.extensin linkage and release of 1,772,871 8/1930 MacClatchie... 166/70 P from the P g Contamer the 2,664,163 12/1953 Schnitter 166/70 Casmg Strmg- 2,870,842 l/l959 Hall 166/70 3,322,l97 5/1967 Baker et a]. 166/70 3,444,928 5/1969 Pitts 166/70 Primary Examiner-James A. Leppink Attorney, Agent, or FirmJohn H. Tre'goning 8 Claims, 7 Drawing Figures CEMENTING PLUG RELEASE ASSIST APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates' generally to improvements in well cementing, and more particularly. but not by way of limitation, to apparatus employed in the release of cementing plugs during the cementing of a casing string or'the like in an oil or gas well.

2. Description of the Prior Art The prior art contains teachings of continuous cementing head plug containers for use in cementing casing strings in oil or gas well boreholes. These devices provide a fluid inlet connection to a source of pressurized displacement fluid and cement slurry. They also provide a cavity within the plug container positioned above the fluid inlet for holding a top cementing plug until such time as it is desired to release the top cementing plug to follow the cement slurry down through the casing string and separate the cement slurry from the displacement fluid above the top plug.

Conditions occasionally exist during the cementing of easing wherein the plug container remains full of fluid at the time of intended release of the top cementing plug. The usual single plug continuous cementing head relies upon gravity and the vacuum provided by the heavy cement slurry within the casing string to withdraw the cementing plug from the upper end of the cementing head below the fluid inlet so that it can be pumped down through the casing string on top of the cement slurry column. It has been found that often when fluidremains in the plug container at the time of intended release of the top plug, the plug is not released at the proper time and proper separation of the displacement fluid from the cement slurry is not obtained.

The present invention provides apparatus for assisting in the release of the top cementing plug so that the release of the plug will be obtained at the precise intended time thereby minimizing the possibility of mixing of the displacement fluid and the cementing slurry during the cementing operation. The present invention further provides a positive indication that the top plug has been released as intended.

SUMMARY OF THE INVENTION The present invention contemplates an apparatus for assisting in the release of a cementing plug within an oil well cementing plug container of the type which includes a closed tubular body having an upper end portion, a lower end portion for communication with the upper end of a casing string, a substantially cylindrical cavity formed in the body communicating with the lower end portion,'a fluid inlet formed in the body intermediate the upper and lower end portions and communicating with the cavity, a plug retaining and releasing pin alternately insertable into the cavity and removable therefrom to support the cementing plug in the cavity above the fluid inlet, and, alternately, release the cementing plug. The apparatus comprises a tubular body member having an upper end portion, a lower end portion and a longitudinal passageway extending therethrough and intersecting the upper and lower end portions thereof. The apparatus also includes means formed on the tubular body member for securing the tubular body member in the upper end portion of the cementing plug container with the longitudinal passageway of the tubular body member communicating with the cylindrical cavity in the plug container in substantial coaxial alignment therewith. The apparatus further includes elongated rod member means, having upper and lower end portions, slidably disposed within the passageway of the tubular body member for longitudinal sliding movement between a lower position and an upper position within the tubular body member, seal means carried within the longitudinal passageway of the tubular body member for providing a sliding seal between the tubular body member and the rod member means, and biasing means interposed between the tubular body member and the elongated rod member means for urging the rod member means upwardly within the body member.

The apparatus further comprises extendable scissors linkage means, having an upper end, a lower end and a medial portion intermediate the upper and lower ends, with the upper end thereof pivotally secured to the lower end portion of the elongated rod member means and the medial portion pivotally secured to the lower end portion of thevtubular body member, for extending the lower end of the linkage means downwardly relative to the body member in response to upward movement of the rod member means relative to the body member by the biasing means and, alternately, retracting the lower end of the linkage means upwardly relative to the body member in response to downward movement of the rod member means relative to the body member against the urging of the biasing means. The apparatus also includes plug contacting means on the lower end of the extendable scissors linkage means for contacting the cementing plug in the cementing plug container and propelling the cementing plug downwardly within the cylindrical cavity ofthe cementing plug container in response to the extending of the lower end of the linkage means downwardly, and rod retaining and releasing means mutually engageable between the tubular body member and the elongated rod member means for retaining the rod member means in the lower position of the tubular body member against the urging of the biasing means and, alternately, releasing the rod member means for upward movement in the tubular body member to the upper position in the tubular body member in response to the urging of the brasing means.

An object of the present invention is to increase the efficiency of oil and gas well casing string cementing operations.

Another object of the invention is to provide apparatus for assisting in the precise release of a cementing plug from within acementing plug container during a cementing operation.

A further object of the invention is to provide a cementing plug release assist apparatus capable of providing a positive visual indication when the cementing plug has been released from the plug container.

A still further object of the invention is to provide a cementing plug release assist apparatus which is economical in construction and reliable in operation.

Other objects and advantages of the present invention will be evident from the following detailed description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectional view of a continuous cementing head plug container with the present invention installed therein in the retracted plug retaining position.

FIG. 2 is a partial cross-sectional view of a continuous cementing head plug container with the cementing plug release assist apparatus installed therein in the extended plug releasing position. I

FIG. 3 is a partial cross-sectional view of the cementing plug release assist apparatus in the retracted position.

FIG. 4 is a partial cross-sectional view of the cementing plug release assist apparatus in the extended position.

FIG. 5 is a cross-sectional view taken along line 55 of FIG. 3. 7

FIG. 6 is a cross-sectional view taken along line 6--6 of FIG. 3.

FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, the cementing plug release assist apparatus of the present invention is generally designated by the reference character 10. In FIGS. 1 and 2 the apparatus 10 is shown installed in a continuous cementing head plug container 12 carrying a typical five wiper cementing top plug 14 therein upon which the apparatus 10 acts.

The continuous cementing head plug container 12 comprises a closed tubular body 16 having an upper end portion 18 and a lower end portion 20 for communication with the upper end of a casing string 22 preparatory to the cementing of the casing string in an oil or gas well. A substantially cylindrical cavity 24 is formed within the tubular body 16 communicating with the lower end-portion 20 thereof in coaxial alignment with the casing string. The fluid inlet 26 is formed in the body 16 intermediate the upper and lower end portions 18 and 20 and provides communication between the cavity 24 and a source of pressurized fluid, not shown. The fluid inlet 26 provides a fluid flow path through the cylindrical cavity 24 into the casing string for various pressurized displacement fluids and for the cement slurry employed during the cementing operation.

A plug retaining and releasing pin assembly 28 is mounted on the continuous cementing head plug container l2 and provides means for alternately retaining and releasing the cementing top plug 14 from a position within the cavity 24 immediately above the intersection of the fluid inlet 26 with the cylindrical cavity 24. The plug retaining and releasing pin assembly 28 includes a substantially cylindrical pin 30 which may be alternately extended into the cavity 24 and retracted therefrom through the action of a control wheel 32 threadedly secured to the cylindrical pin 30.

An internally threaded aperture 34 is formed in the upper end portion 18 of the tubular body 16 in substantial coaxial alignment with the cylindrical cavity 24. The internally threaded aperture 34 provides means for securing the cementing plug release assist apparatus 10 to the cementing head plug container 12.

Referring now to FIGS. 3--7, the construction of the cementing plug release assist apparatus 10 will be described in detail. The apparatus 10 includes a tubular body member assembly 36 having an upper end portion 38, a lower end portion and a medial portion 42 intermediate the upper and lower end portions 38 and 40. A longitudinal passageway 44 extends through the body member assembly 36 intersecting the upper and lower end portions 38 and 40 thereof. The longitudinal passageway 44 includes a longitudinal cylindrical bore 46 formed in the medial portion 42 of the body member 36 and having a pair of annular grooves 48 formed therein in which a pair of suitable annular seals 50, such as O-rings, are respectively positioned.

A counterbore 52 is formed in the longitudinal passageway 44 from the upper end portion 38 of the tubular body 36 forming a cylindrical surface 54 and an annular shoulder 56 interconnecting the surface 54 and the cylindrical bore 46. The longitudinal passageway 44 also includes a cylindrical portion 58 formed in the medial portion 42 of the tubular body member assembly 36 intermediate the cylindrical bore 46 and the lower end portion 40 of the body member assembly 36 and having a diameter greater than the diameter of the cylindrical bore 46.

The medial portion 42 of the body member assembly 36 includes an externally threaded portion 60 formed thereon for threaded engagement with the internally threaded aperture 34 of the cementing head plug container 12 described above. Wrench flats 62 are formed on the medial portion 42 above the externally threaded portion 60 to facilitate the threaded engagement of the body member assembly 36 to the cementing head plug container 12. The portion of the medial portion 42 of the body member assembly 36 carrying the wrench flats 62 is preferably hexagonal in cross-section.

The lower end portion 40 of the tubular body member assembly 36 comprises a bifurcated cylindrical portion 64 secured at the upper end portion 66 thereof within the cylindrical portion 58 of the longitudinal passageway 44. The bifurcated cylindrical portion 64 includes an interrupted internal cylindrical surface 68 formed therein in longitudinal alignment with and forming a portion of the longitudinal passageway 44. The interrupted cylindrical surface 68 terminates at its lower end in an interrupted annular shoulder 70.

The upper end portion 38 of the tubular body member assembly 36 includes a pair of longitudinally aligned slot or windows 72 formed therein communicating between the longitudinal passageway 44 and the exterior thereof. The slots 72 are positioned diammetrically opposed to one another. A transverse bore 74 is formed in the upper end portion 38 and is sized to receive a detent ball lock pin 76 therethrough as will be described more fully hereinafter. The detent ball lock pin 76 is conveniently secured to the upper end portion 38 by means of a suitable chain 78 and ring 80.

An elongated rod member 82 having an upper end portion 84, a lower end portion 86 and a cylindrical medial portion 88 is slidably disposed within the longitudinal passageway 44 with the medial portion 88 in sliding sealing engagement with the annular seals 50 carried by bore 46 in the medial portion 42 of the tubular body member assembly 36. A downwardly facing annular shoulder 90 is formed on the upper end portion 84. A helical compression spring 92 is disposed coaxially about the elongated rod member 82 with the upper end portion 94 thereof engaging the downwardly facing annular shoulder 90 and with the lower end portion 96 thereof engaging the annular shoulder 56 of the tubular body member assembly 36. The helical compression spring 92 provides biasing means for urging the rod member 82 upwardlyrelative to the body member assembly 36. t

The lower end portion 86 of the elongated rod member 82 includes a cylindrical outer periphery 98 slidably received within the interrupted internal cylindrical surface 68 of the bifurcated cylindrical portion 64 of the tubular body member assembly 36. The lower end portion 86 also includes a downwardly extending bifurcated portion 100.

An extendable scissors linkage assembly 102 is pivotally secured at its upper end portion 104 to the bifurcated portion 100 of the elongated rod member 82 by means of a transverse pin or bolt 106 extending there through. The medial portion 108 ofthe extendable scissors linkage assembly 102 is pivotally secured to the bifurcated cylindrical portion 64 of the lower end portion 40 of the tubular body assembly 36 by means of a transverse pin or ,bolt 110 extending therethrough. The lower end portion. 112 of the extendable scissors linkage assembly 102 is privotally secured to a plug contacting shoe 114 by means of a transverse pin or bolt 116 extending therethrough. The plug contacting shoe 114 includes a substantially flat plug contacting surface 118 formed on the bottom thereof.

The extendable scissors linkage assembly 102 is constructed of a plurality of long rigid links 120 pivotally secured together by means of transverse pins or bolts 122.,Short rigid links 124 provide interconnection between the twouppermost long rigid links 120 to the bifurcated portion 100 of the elongated rod member 82 by means of the previously mentioned transverse pin or bolt 106. The short rigid links 124 are respectively pivotally secured to the uppermost long rigid links 120 by means of two additional transverse pins or bolts 122. Two additional short rigid links 126 provide interconnection between the lowermost long rigid links 120 and the plug contacting shoe 114 by means of the previously mentioned transverse pin or bolt 116. The short rigid links 126 are respectively pivotally secured to the lowermost long rigid links 120 by means of two additional transverse pins or bolts 122.

Preferably, the uppermost pair of long rigid links 120 of the extendable scissors linkage assembly 102 is pivotally secured -to the bifurcated cylindrical portion 64 by the transverse pin or bolt 110 as shown in the drawings. While only one additional pair of long rigid links 120 is illustrated in the drawings, it will be readily understood that, depending on the amount of longitudinal travel desired for the plug contacting shoe 114, additional pairs of long rigid links 120 may be added to the extendable scissors linkage assembly 102 between the medial portion 108 and the plug contacting shoe 114 to proportionately increase the longitudinal travel distance of the plug contacting shoe 114 during extension of the linkage assembly 102. As shown in FIGS. 5-7, washers 128, formed of a suitable material such as nylon, may be advantageously employed in the construction of the extendable scissors linkage assembly 102 by positioning them'respectively between adjacent rigid links of the previously described pivotal pin connections therebetween.

Operation of the Preferred Embodiment In operation, the cementing plug release assist apparatus is threadedly secured into the internally threaded aperture 34 in the upper end portion 18 of the continuous cementing head plug container 12 as shown in FIGS. 1 and 2. The elongated rod member 82 is forced downwardly against the upper bias of the helical compression spring 92 thereby retracting the extendable scissors linkage assembly 102 as shown in H08. 1 and 2. The elongated rod member 82 is retained in its lower or cocked position by means of the detent ball lock pin 76 extending through the transverse bore 74 in the upper end portion 38 of the tubular body member assembly 36, thereby preventing upward movement of the elongated rod member 82 as shown in FIG. 1.

The cementing top plug 14 is positioned within the continuous cementing head plug container 12 above the fluid inlet 26 and is retained in this position by means of the pin 30 of the plug retaining and releasing pin assembly 28, as shown in FIG. 1.

When it is desired to release and launch the cementing top plug 14 to follow the column of cement slurry downwardly from the cementing head plug container 12 into the casing string ahead of the pressurized displacement fluid, the cylindrical pin 30 is retracted from the cylindrical cavity 24 of the plug container 12 by rotation of the control wheel 32 of the plug retaining and releasing pin assembly 28. When the pin 30 is completely withdrawn from the cylindrical cavity 24, the detent ball lock pin 76 is withdrawn from the transverse bore 74 through the upper end portion 38 of the tubular body member assembly 36. Immediately upon the withdrawal of the detent ball lock pin 76 from the transverse bore 74, the helical compression spring 92 drives the elongated rod member 82 upwardly relative to the tubular body member assembly 36 thereby extending the extendable scissors linkage assembly 102 and driving the plug containing shoe 114 downwardly to provide a positive cementing plug rlease assist thereby assuring that the cementing top plug 14 is launched at the proper time intermediate the column of cement slurry and the pressurized displacement fluid. The upward force applied to the rod member 82 includes the force component provided by the spring 92 and further includes a supplementary upward force component provided by the hydraulic pressure differential of the pressurized displacement fluid and cement slurry acting on the cross-sectional area of the medial portion 88 of the rod member 82.

A visual indication'of the positive release and launch of the cementing top plug 14 is provided when the upper end portion 84 of the elongated rod member 82 is visible through the uppermost ends of the slots or windows 72 formed in the upper end portion 38 of the tubular body member assembly 36, as shown in FIGS. 2 and 4.

Changes may be made in the combination and arrangement of parts or elements as set forth in the specification and illustrated in the drawings without departing from the spirit and scope of the invention as defined in the following claims.

What is claimed is:

1. Apparatus for assisting in the release of a cementing plug within a cementing plug container of the type which includes a closed tubular body having an upper end portion, a lower end portion for communication with the upper end of a casing string, a substantially cylindrical cavity formed in the body communicating with the lower end portion, a fluid inlet formed in the body intermediate the upper and lower end portions and communicating with the cavity, a plug retaining and re leasing pin alternately insertable into the cavity and removable therefrom to support the cementing plug in the cavity above the fluid inlet, and, alternately, release the cementing plug, comprising:

a body member having an upper end portion and lower end portion and a longitudinal passageway extending therethrough and intersecting the upper and lower end portions thereof;

means formed on said body member for securing said body member in the upper end portion of the cementing plug container with the longitudinal passageway of said body member communicating with the cylindrical cavity in the plug container in substantial alignment therewith;

rod member means, having upper and lower end portions, movably disposed within the passageway of said body member for longitudinal movement between a lower position and an upper position in said body member;

seal means carried by said body member for providing a seal between said body member and said rod member means;

biasing means interposed between said body member and said rod member means for urging said rod member means upwardly relative to said body member;

extendable linkage means, having an upper end, a lower end and a medial portion intermediate the upper and lower ends, with the upper end thereof secured to the lower end portion of said rod member means and the medial portion secured to the lower end portion of said body member, for extending the lower end of said linkage means downwardly relative to said body member in response to upward movement of said rod member means relative to said body member;

plug contacting means on the lower end of said extendable linkage means for contacting the cementing plug in the cementing plug container and moving the cementing plug downwardly within the cylindrical cavity of the cementing plug container in response to the extending of the lower end of said linkage means downwardly; and

rod retaining and releasing means mutually engageable between said body member and said rod member means for retaining said rod member means in the lower position in said tubular body member against the urging of said biasing means and, alternately, releasing said rod member means for upward movement in said body member to the upper position in said body member.

2. Apparatus for assisting in the release of a cementing plug within an oil well cementing plug container of the type which includes a closed tubular body having an upper end portion, a lower end portion for communication with the upper end of a casing string, a substantially cylindrical cavity formed in the body communicating with the lower end portion, a fluid inlet formed in the body intermediate the upper and lower end portions and communicating with the cavity, a plug retaining and releasing pin alternately insertable into the cavity and removable therefrom to support the cementing plug in the cavity above the fluid inlet, and, alternately, release the cementing plug, comprising:

a tubular body member having an upper end portion and lower end portion and a longitudinal passageway extending therethrough and intersecting the upper and lower end portions thereof;

means formed on said tubular body member for securing said tubular body member in the upper end portion of the cementing plug container with the longitudinal passageway of said tubular body member communicating with the cylindrical cavity in the plug container in substantial coaxial alignment therewith;

elongated rod member means, having upper and lower end portions, slidably disposed within the passageway of said tubular body member for longitudinal sliding movement between a lower position and an upper position within said tubular body member;

seal means carried within the longitudinal passageway of said tubular body member for providing a sliding seal between said tubular body member and said rod member means;

biasing means interposed between said tubular body member and said elongated rod member means for urging said rod member means upwardly within said body member;

extendable scissors linkage means, having an upper end, a lower end and a medial portion intermediate the upper and lower ends, with the upper end thereof pivotally secured to the lower end portion of said elongated rod member means and the medial portion pivotally secured to the lower end portion of said tubular body member, for extending the lower end of said linkage means downwardly relative to said body member in response to upward movement of said rod member means relative to said body member by said biasing means and, alternately, retracting the lower end of said linkage means upwardly relative to said body member in response to downward movement of said rod member means relative to said body member against the urging of said biasing means;

plug contacting means on the lower end of said extendable scissors linkage means for contacting the cementing plug in the cementing plug container and moving the cementing plug downwardly within the cylindrical cavity of the cementing plug container in response to the extending of the lower end of said linkage means downwardly; and

rod retaining and releasing means mutually engageable between said tubular body member and said elongated rod member means for retaining said rod member means in the lower position in said tubular body member against the urging of said biasing means and, alternately, releasing said rod member means for upward movement in said tubular body member to the upper position in said tubular body member in response to the urging of said biasing means.

3. The apparatus as defined in claim 2 wherein said biasing means is characterized further to include:

a helical compression spring having an upper end portion engaging the upper end portion of said elongated rod member means and having a lower end portion engaging said tubular body member.

4. The apparatus as defined in claim 2 wherein said extendable scissors linkage means comprises:

a plurality of rigid links pivotally secured to one another by means of a plurality of transverse pins. with the uppermost rigid links being pivotally secured by a first transverse pin to the lower end portion of said elongated rod member means and the of upward movement of said rod member means relative to said body member.

6. The apparatus as defined in claim 2 characterized further to include:

indicating means carried by said tubular body member for providing a visual indication when said elongated rod member 'means has been moved upwardly by said biasing means relative to said body member.

7. The apparatus as defined in claim 2 wherein said means formed 'on said tubular body member for securing said tubular body member in the upper end portion of the cementing plug container is characterized further to include:

external threads formed on said tubular body member; and

wrench flats formed on the exterior of said tubular body member adjacent to said external threads.

8. The apparatus as defined in claim 2 wherein said rod retaining and releasing means is characterized further to include:

a transverse bore formed in the upper end portion of said tubular body member; and

lock pin means sized and shaped to be received within said transverse bore for insertion therethrough above the upper end portion of said elongated rod member means and, alternately, removal therefrom. 

1. Apparatus for assisting in the release of a cementing plug within a cementing plug container of the type which includes a closed tubular body having an upper end portion, a lower end portion for communication with the upper end of a casing string, a substantially cylindrical cavity formed in the body communicating with the lower end portion, a fluid inlet formed in the body intermediate the upper and lower end portions and communicating with the cavity, a plug retaining and releasing pin alternately insertable into the cavity and removable therefrom to support the cementing plug in the cavity above the fluid inlet, and, alternately, release the cementing plug, comprising: a body member having an upper end portion and lower end portion and a longitudinal passageway extending therethrough and intersecting the upper and lower end portions thereof; means formed on said body member for securing said body member in the upper end portion of the cementing plug container with the longitudinal passageway of said body member communicating with the cylindrical cavity in the plug container in substantial alignment therewith; rod member means, having upper and lower end portions, movably disposed within the passageway of said body member for longitudinal movement between a lower position and an upper position in said body member; seal means carried by said body member for providing a seal between said body member and said rod member means; biasing means interposed between said body member and said rod member means for urging said rod member means upwardly relative to said body member; extendable linkage means, having an upper end, a lower end and a medial portion intermediate the upper and lower ends, with the upper end thereof secured to the lower end portion of said rod member means and the medial portion secured to the lower end portion of said body member, for extending the lower end of said linkage means downwardly relative to said body member in response to upward movement of said rod member means relative to said body member; plug contacting means on the lower end of said extendable linkage means for contacting the cementing plug in the cementing plug container and moving the cementing plug downwardly within the cylindrical cavity of the cementing plug container in response to the extending of the lower end of said linkage means downwardly; and rod retaining and releasing means mutually engageable between said body member and said rod member means for retaining said rod member means in the lower position in said tubular body member against the urging of said biasing means and, alternately, releasing said rod member means for upward movement in said body member to the upper position in said body member.
 2. Apparatus for assisting in the release of a cementing plug within an oil well cementing plug container of the type which includes a closed tubular body having an upper end portion, a lower end portion for communication with The upper end of a casing string, a substantially cylindrical cavity formed in the body communicating with the lower end portion, a fluid inlet formed in the body intermediate the upper and lower end portions and communicating with the cavity, a plug retaining and releasing pin alternately insertable into the cavity and removable therefrom to support the cementing plug in the cavity above the fluid inlet, and, alternately, release the cementing plug, comprising: a tubular body member having an upper end portion and lower end portion and a longitudinal passageway extending therethrough and intersecting the upper and lower end portions thereof; means formed on said tubular body member for securing said tubular body member in the upper end portion of the cementing plug container with the longitudinal passageway of said tubular body member communicating with the cylindrical cavity in the plug container in substantial coaxial alignment therewith; elongated rod member means, having upper and lower end portions, slidably disposed within the passageway of said tubular body member for longitudinal sliding movement between a lower position and an upper position within said tubular body member; seal means carried within the longitudinal passageway of said tubular body member for providing a sliding seal between said tubular body member and said rod member means; biasing means interposed between said tubular body member and said elongated rod member means for urging said rod member means upwardly within said body member; extendable scissors linkage means, having an upper end, a lower end and a medial portion intermediate the upper and lower ends, with the upper end thereof pivotally secured to the lower end portion of said elongated rod member means and the medial portion pivotally secured to the lower end portion of said tubular body member, for extending the lower end of said linkage means downwardly relative to said body member in response to upward movement of said rod member means relative to said body member by said biasing means and, alternately, retracting the lower end of said linkage means upwardly relative to said body member in response to downward movement of said rod member means relative to said body member against the urging of said biasing means; plug contacting means on the lower end of said extendable scissors linkage means for contacting the cementing plug in the cementing plug container and moving the cementing plug downwardly within the cylindrical cavity of the cementing plug container in response to the extending of the lower end of said linkage means downwardly; and rod retaining and releasing means mutually engageable between said tubular body member and said elongated rod member means for retaining said rod member means in the lower position in said tubular body member against the urging of said biasing means and, alternately, releasing said rod member means for upward movement in said tubular body member to the upper position in said tubular body member in response to the urging of said biasing means.
 3. The apparatus as defined in claim 2 wherein said biasing means is characterized further to include: a helical compression spring having an upper end portion engaging the upper end portion of said elongated rod member means and having a lower end portion engaging said tubular body member.
 4. The apparatus as defined in claim 2 wherein said extendable scissors linkage means comprises: a plurality of rigid links pivotally secured to one another by means of a plurality of transverse pins, with the uppermost rigid links being pivotally secured by a first transverse pin to the lower end portion of said elongated rod member means and the lowermost rigid links being pivotally secured to said plug contacting means by a second transverse pin, and with a pair of rigid links, positioned intermediate the uppermost and lowermost rigid links, being pivotally secured to the lower end portion of said tubular body Member by means of a third transverse pin.
 5. The apparatus as defined in claim 2 wherein the lower end of said linkage means extends downwardly relative to said body member in response to the upward movement of said rod member relative to said body member a longitudinal distance greater than the length of upward movement of said rod member means relative to said body member.
 6. The apparatus as defined in claim 2 characterized further to include: indicating means carried by said tubular body member for providing a visual indication when said elongated rod member means has been moved upwardly by said biasing means relative to said body member.
 7. The apparatus as defined in claim 2 wherein said means formed on said tubular body member for securing said tubular body member in the upper end portion of the cementing plug container is characterized further to include: external threads formed on said tubular body member; and wrench flats formed on the exterior of said tubular body member adjacent to said external threads.
 8. The apparatus as defined in claim 2 wherein said rod retaining and releasing means is characterized further to include: a transverse bore formed in the upper end portion of said tubular body member; and lock pin means sized and shaped to be received within said transverse bore for insertion therethrough above the upper end portion of said elongated rod member means and, alternately, removal therefrom. 